Conventional laundering techniques for cleaning and refreshing (e.g., removing malodors) fabric articles can be generally categorized into the aqueous-based washing technique and the “dry cleaning” technique. The former involves immersion of the fabric article in a solution comprising primarily of water; detergent or soap may be added to enhance the cleaning function. The latter typically involves the use of non-aqueous fluids as the agent for cleaning and refreshing.
Cleaning solvents, after being used in a laundering treatment, typically comprise contaminants, such as dyes, water and/or surfactants. Since the dry cleaning solvents are more expensive than water, there is a need to recycle/reuse the dry cleaning solvents in more than one treatment.
Conventional dry cleaning solvents are subjected to a distillation method to remove some contaminants. Representative systems using the distillation method are disclosed in EP 543,665 and U.S. Pat. Nos. 5,942,007; 6,056,789; 6,059,845; and 6,086,635. However, equipment and conditions to run the distillation are extremely burdensome as well as energy consuming. Among the drawbacks of the distillation method are the high cost of the distillation unit, the daily manual intervention required to clean the still bottom, and its ineffectiveness in removing volatile contamninants. Accordingly, there is a need to remove contaminants from dry cleaning solvents without distillation.
There have been other methods to remove contaminants from dry cleaning solvents without distillation. Typically, these non-distillation methods use filtration only systems with adsorbent materials, such as activated carbons and/or clay. For example, the commonly used, commercially available KleenRite® filter is made of a clay absorbent and an activated carbon adsorbent. Representative filters containing carbon and clay adsorbent materials are disclosed in U.S. Pat. Nos. 4,277,336 and 3,658,459. However, such filter has a rather limited lifetime due to the high percentage of clay absorbent in the filter. The clay absorbent has a finite capacity for absorbing contaminants, such as water, and once that capacity is met, the filter must be replaced with a new filter. In addition to the limitations around the clay absorbent, the activated carbon adsorbent has limitations also. The particle size and/or pore size of the activated carbon adsorbent material allows some contaminants to flow past the activated carbon adsorbent material, thus making the filter ineffective. Further, in conventional use, the used, contaminated dry cleaning solvent is pumped through the filter at a rate that does not allow the clay absorbent and/or activated carbon adsorbent to remove contaminants effectively. This is especially true for those contaminants that are highly soluble in the dry cleaning solvent. Additionally, some of the solvents are lost due to the frequent changes of the filters.
Therefore, there is a need for a method that effectively removes contaminants from a dry cleaning solvent such that the purified solvent can be recycled/reused.
It is also desirable to have a method capable of purifying a dry cleaning solvent in an economical and energy efficient manner.
Additionally, it is desirable that the purification method is safe and durable. The purification system or unit must have a lifetime of at least 25 cycles before operator intervention and/or changing of components become necessary.
Therefore, there is a need for a purification method that removes soluble contaminants from the dry cleaning solvent.